Foursquare's Dennis Crowley on Building a Massive Community

If you've "checked in" to an urban hotspot, say thank you to Dennis Crowley, the 36-year-old co-founder of location-based social tool Foursquare.

Using Foursquare's smartphone app, users can discover local businesses and places to go, and share their discoveries and whereabouts with friends -- often while earning badges and saving money through special offers. Foursquare says it has 20 million registered users and works with more than 750,000 businesses, large and small.

In 2010, about a year after launching Foursquare, Crowley turned down separate acquisition offers from tech giants Facebook and Yahoo!. Foursquare's most recent round of financing -- $50 million last year from Andreessen Horowitz, among other groups -- reportedly valued the company at $600 million.

We sat down with Crowley to discuss what makes a tech startup great. What follows is an edited version of our conversation:

Entrepreneur: What sets apart successful startups that attract millions of consumers from those that never really get off the ground?Crowley: Whether it's Google or Twitter or Facebook, they all add something to the way that I share content or solve problems in my everyday life.

We built Foursquare literally for ourselves and for our group of 10 friends. And it turns out that when you build things that 10 of your friends like, their friends like them and their friends like them -- and then you suddenly get to millions of users.

Entrepreneur: How do you generate ideas and figure out which ones to pursue?Crowley: I've worked at companies where the ideas come from the top down, and you build what you're told to build. That probably works for some companies.

We're different because we've hired so many rock stars. No one wants to be the guy that just sits there and is executing on someone else's ideas. We have to think up these different ways of allowing people to get their ideas out there.

Entrepreneur: How does an entrepreneur know when to sell? Did you make the right call by not selling to Facebook or Yahoo?Crowley: I got some advice a while ago that, if you can't see where the ride is going to end, then you don't want to get off of it. We have our own vision of what the finish line looks like and what the product looks like a year from now. That idea is different from what Google is chasing and different from what Facebook is chasing.

That's the thing that we can do better than anyone else: execute on our ideas. That's the focus that we need to have to be successful.

Entrepreneur: What's your advice for tech entrepreneurs who want to build something big?Crowley: For a long time, we had these ideas for things we wanted to build, and we listened to people tell us that the ideas were silly or stupid or weren't going to work.

You can't listen to them, and you really have to build this stuff on your own. Prove to yourself that it's either a good idea or it's not. …You have to be totally fine with throwing things away and realizing you might have to throw away five before you find one good thing.